1. Field of the Invention
This invention relates to battery-powered electronic devices. More specifically, it relates to a battery replacement system for battery-powered digital data handling devices.
2. Description of the Prior Art
When the battery in a battery-operated computer becomes discharged while the computer is in use, the battery has to be replaced. To replace the battery in prior art systems, the following steps ordinarily had to be taken:
(a) Save the work file. PA0 (b) Exit the current program. PA0 (c) Turn the computer off. PA0 (d) Remove the discharged battery. PA0 (e) Replace with a new battery. PA0 (f) Apply power to the computer. PA0 (g) Wait for the power-up sequences of tests and initialization. PA0 (h) Invoke the current program. PA0 (i) Load the work file.
This prior art procedure can take appreciable time, depending on the complexity of the program.
To overcome the disadvantages of this procedure, prior art lap-top computers have made use of a special memory for storing the contents of the main memory and also that of the contents of the internal registers of the microprocessor component of the computer. This special memory is a very low-powered, expensive static-type memory typically limited, by cost, to approximately 640 K bytes. As battery-powered computers have become more complex, the memory size has increased to where those computers with 640 K bytes are impractical since the state-of-the-art capacity is now up to 8 megabytes. Static memory of this size would be prohibitive in cost and would be physically too large.
Another prior art system is involved with writing the contents of the registers and the main memory into a disk memory before the computer is shut down for battery replacement. However, the power requirement in that type of system is high and, furthermore, all of the registers in the current microprocessor structures are not susceptible of being read out and preserved. Therefore, the exact state of the microprocessor cannot be saved before turning the power off for battery replacement.
According to the present invention, the power is maintained throughout the battery replacement process, insuring preservation of all memory and contents of operational registers.